Abstract Some novel chiral ligands, (S)‐(+) 1‐substituted aryl‐4‐(1‐phenyl) ethylformamido‐5‐amino‐1,2,3‐triazoles, were prepared starting from 1‐substituted aryl‐4‐ethoxycarbonyl‐5‐amino‐1,2,3‐triazoles and other reagents. They were used as catalytic chiral ligands in the silver (I)‐promoted enantioselective allylation reaction of aldehydes with allyltributyltin.
Since the 1970's stratospheric zone attenuation liable for surface UV radiation enhancement has been among the ever-increasing concerns of global climatologists. In recent years, numerous efforts have been undertaken at home and abroad to investigate the effect of enhanced surface UV-B on crops' growth, development and yield formation, achieving a lot of significant fruits and concurrently on field ecosystems. As we know, most of the experiments in the past were conducted in laboratories, including a short-term response on an individual-plant basis. This condition differs consipicuously from yield experiments at the level of an ecosystem with regard to its long-range response. Specifically the degree to which the UV radiation influences non-crop species, which leads to the distortion of the response to UV-B enhancement of crop's population and its ecosystem. As a result, it is necessary to carry out long-range field experiments at an ecosystem's level. This paper aims at the impacts of intensified UV-B upon weeds and large soil worms (i.e., microanimals) in an ecosystem of growing wheat, corn (maize) and spinach together with preliminary investigation of the mechanisms.
Consecutive droughts that have occurred in the Canadian prairies have resulted in significant economic losses, ecological degradation, and environmental deterioration. The purpose of this study was to investigate the efficiency of remotely sensed data on drought assessment combined with climate data. The study area was the Canadian prairie ecozone in the provinces of Alberta, Saskatchewan, and Manitoba. There objectives were five-fold: 1) comparing Kriging and inverse distance weighting (IDW) interpolation methods, 2) comparing four spectral variables, the normalized difference vegetation index (NDVI), the enhanced vegetation index (EVI), the red and the mid infrared (MIR), 3) comparing three moisture indices (P-PET, P/PET and (P-PET/PET), 4) evaluating the relationships between spectral variables and moisture indices, and 5) assessing drought effects on different ecoregions. Results showed that there is no significant difference between Kriging and IDW, the two interpolation methods. MODIS vegetation indices could effectively assess drought conditions, especially EVI. Among the moisture indices compared, P-PET showed a better result. The impacts of droughts vary from year to year and from ecoregion to ecoregion. Aspen Parkland has higher drought resistance because of tree components.
Taking winter wheat Triticum aestivum L. (cv. Yangmai 13) as test material, a field experiment was conducted in Nanjing City to study the effects of simulated reduced solar radiation on the diurnal variation of winter wheat flag leaf photosynthetic rate and the main affecting factors. Five treatments were installed, i. e., 15% (T15), 20% (T20) , 40% (T40), 60% (T60), and 100% (CK) of total incident solar radiation. Reduced solar irradiance increased the chlorophyll and lutein contents significantly, but decreased the net photosynthetic rate (Pn). Under different solar irradiance, the diurnal variation of Pn had greater difference, and the daily maximum Pn was in the order of CK > T60 > T40 > T 20 > T15. In CK, the Pn exhibited a double peak diurnal curve; while in the other four treatments, the Pn showed a single peak curve, and the peak was lagged behind that of CK. Correlation analysis showed that reduced solar irradiance was the main factor affecting the diurnal variation of Pn, but the physiological parameters also played important roles in determining the diurnal variation of Pn. In treatments T60 and T40, the photosynthesis active radiation (PAR), leaf temperature (T1) , stomatal conductance (Gs) , and transpiration rate (Tr) were significantly positively correlated with Pn, suggesting their positive effects on Pn. The intercellular CO2 concentration (Ci) and stomatal limitation (Ls) had significant negative correlations with Pn in treatments T60 and T40 but significant positive correlations with Pn in treatments T20 and T15, implying that the Ci and Ls had negative (or positive) effects on Pn when the solar irradiance was higher (or lower) than 40% of incident solar irradiance.
The Agricultural Production Systems Simulator (APSIM) was applied to simulate the 1999-2001 field experimental data and the 2002-2003 water use data at the Yucheng Experiment Station under Chinese Ecosystem Research Network, aimed to verify the applicability of the model to the wheat-summer maize continuous cropping system in North China Plain. The results showed that the average errors of the simulations of leaf area index (LAI), biomass, and soil moisture content in 1999-2000 and 2000-2001 field experiments were 27.61%, 24.59% and 7.68%, and 32.65%, 35.95% and 10.26%, respectively, and those of LAI and biomass on the soils with high and low moisture content in 2002-2003 were 26.65% and 14.52%, and 23.91% and 27.93%, respectively. The simulations of LAI and biomass accorded well with the measured values, with the coefficients of determination being > 0.85 in 1999-2000 and 2002-2003, and 0.78 in 2000-2001, indicating that APSIM had a good applicability in modeling the crop biomass and soil moisture content in the continuous cropping system, but the simulation error of LAI was a little larger.
A continuing 26-hour monitoring is given on the physical and chemical indicators of the water around the Potamogeton crispus population in Xuanwu Lake, Nanjing City to study the consequent environmental effects. The result shows that both the highest (11.85 mg/L) and the lowest (9.90 mg/L) DO concentrations occur in the population, while the DO concentration decreases with increasing distance from the population. The DO concentration difference of the surface and bottom waters within the population and the open waters is slight, yet it is more obvious in the junction between the population and the open waters. The pH value declines from the population to the open waters. The maximum pH value of the surface water within the population is 10.3, and the minimum value outside the population is 9.2. The pH value of surface water is higher than the bottom within the population, but there is no such difference in the open waters. The TDS content increases with increasing distance from the population, which shows the maximum is 216.9 mg/L of the surface water and the minimum is 177.7 mg/L outside the population. The TDS value of the surface is lower than that in the bottom. The TN, NO2(-) -N, NO3(-) -N contents also increase with the increasing distance from the population, in that the TN content is lower than 2.00 mg/L within the population while the outside is higher than 2.00 mg/L; the NO2(-) -N content is less than 0.026 mg/L within the population while the outside is higher than 0.026 mg/L; the NO3(-) -N content is lower than 1.25 mg/L within the population while the outside is mostly higher than 1.25 mg/L. The TN, NO2(-) -N, NO3(-) -N contents of the surface water are lower than those in the bottom, but the difference is insignificant (p > 0.05). There is no significant difference of the NH4(+) -N content between the inner population and the external and the surface and the bottom. The TP and PO4(3-) -P contents of the surface water are lower than those in the bottom within the population, in that the TP, PO4(3-) -P contents of the highest point of the surface water within the population are 90.9% and 69.64% higher than the lowest point outside the population. The TP and PO4(3-) -P contents of the bottom water are significantly higher than those of the surface within the population, but the difference is slight from outside the population. Therefore, the Potamogeton crispus population plays an important role in improving the lake water quality.
Employing floating static chamber-chromatography method, the N2O diurnal fluxes at the water-air interface of four rivers (Tuanjie River, Jinchuan River, Inner and Outer Qinhuai River) and Jinniu Lake were monitored in Nanjing during summer. The results show that four rivers act as the sources of N2O emission, but Jinniu Lake is characterized by the absorption of N2O. The highest N2O flux from Inner Qinhuai presented at 20:00 because of the changing of hydrodynamic conditions. Both Jinchuan and Tuanjie rivers' minimum N2O fluxes were detected when the content of dissolved oxygen was extremely low. The tendency of N2O from Outer Qinhuai showed a double-peak because of its daytime nitrification and nocturnal denitrification. The flux of N2O from Jinniu Lake had been noted as being generally higher at night than that during light hours due to the effect of wind. For natural rivers, the proper sampling period is from 08:00 to 12:00, but for the river subjected to interference, the sampling period is different.
Stratospheric ozone depletion and enhanced solar ultraviolet-B (UV-B) irradiance may have adverse impacts on the productivity of agricultural crops. Though only a small portion of the total solar electromagnetic spectrum, UV-B irradiance has a disproportionately large photobiological effect, largely because it is readily absorbed by important macromolecules such as proteins and nucleic acids. Numerous investigations have demonstrated that the effect of UV-B enhancements on plants includes a reduction in grain yield, alteration in species competition, susceptibility to disease, and changes in plant structure and pigmentation. Many experiments examining UV-B radiation effects on plants were conducted in growth chambers or greenhouses. It has been questioned if the effect of UV-B radiation on plants can be extrapolated to field responses from indoor studies because of the unnaturally high ratios of UV-B/UV-A and UV-B/PAR in many indoor studies. Field studies on UV-B radiation effect on plants have been recommended in order to use the UV and PAR irradiance provided by natural light. This study found the maize yield formation and yield structural elements responded to enhanced UV-B radiation under field conditions. Enhanced UV-B radiation caused a significant reduction of the dry matter accumulation and the maize grain yield in turn was affected. Analysis of yield structure indicates that the maize yield decreased with increased UV-B radiation and was evidently related to the decreased kernel weight and kernel number per ear.
Some novel chiral ligands (S)-(+) 1-substituted aryl-4-(1-phenyl) ethylformamido -5-amino 1, 2, 3-triazole were prepared starting from 1-substituted aryl-4-ethoxycarbonyl -5-amino-l, 2, 3-triazoles and other reagents.They were used as catalytic chiral ligands in the silver (I)-promoted enantioselective allylation reaction of aldehydes with allyltributyltin.Catalytic asymmetric synthesis is a valuable method for the preparation of optically active substances(l).In this context, the stereoselective addition of organometallics to a carbonyl group has been extensively studied.In particular, the enantioselective allylation of carbonyl compounds is a challenging problem in organic synthesis.Although numerous important examples of the reaction using a stoichiomeric amount of chiral diamine have been reported(2), there is no method available for a catalytic process including chiral diamine having v-triazole.Recently Yamamoto reported a new catalytic enantioselective allylation reaction of aldehydes with allyltributyltin using a BINAP-silver (I) complex as a catalyst (3).To the best of our knowledge, this is the few case using a chiral silver (I) complex in a catalytic asymmetric reaction.This interesting result prompted us to design and synthesize other chiral ligands which are suitable for making chiral silver(I) complexes for catalytic asymmetric reactions.We wanted to try some chiral ligands containing a nitrogen atom because it is well known that nitrogen can easily coordinate to various metals such as Co, Cu, Zn and other metal giving stable chiral metal complexes(4) .Based on this concept, using (S)-(+)-l-phenylethylamine as a chiral scaffold, we started to prepare a series of the chiral (S)-(+) 1-substituted aryl-4-(1-phenyl) ethylformamido-5-amino-l, 2, 3-triazole from 1-substituted aryl-4-ethoxycarbonyl -5-amino-l, 2, 3-triazoles and other reagents.In this paper, we wish to report the results using them as catalytic chiral ligands for silver (I)-promoted enantioselective allylation reaction of various aldehydes with allyltributyltin.
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